栓内层在内部由软木新生层产生的组织。
生长龄不同，额外形成层、栓内层的宽度和细胞大小不同。
Roots are different in the width of supernumerary cambium and phelloderm and the cell.
另外，光皮型杜仲在栓内层分布有较少的，质地紧密的石细胞群；
Secondly, there was a little of collenchyma whose texture was tight in smooth type's endothecium of phellem;
结果：根横切面上栓内层的石细胞环带和次生木质部导管的排列方式、初生木质部为四原型等为显微鉴别特征；
Results:The circular belt of sclereids in the phelloderm, secondary xylem vessel order of the transverse section, and tetrarch of the primary xylem were microscopic characters.
结果：根横切面上栓内层的石细胞环带和次生木质部导管的排列方式、初生木质部为四原型等为显微鉴别特征；
Results:The circular belt of sclereids in the phelloderm, secondary xylem vessel order of the transverse section, and tetrarch of the primary xylem were microscopic characters.
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